Silencer or muffler



Sept. 10, 1963 F. E. DEREMER SILENCER 0R MUFFLER Filed Nov. 9, 1959 United States Patent O g Fired Nov. 9, 1959, ser. No. 851,712 f 4 Claims. (C1. 181-54) rllhis invention relates to sound attenuating or sound absorbing devices and more especially to sound attenuating apparatus, muffler or silencer for use with the exhaust gas system of an internal combustion engine of a vehicle for attenuating or absorbing sound waves entrained in a gas stream.

Muiers or silencers have been employed with exhaust gas streams constructed with interior gas passage tubes in communication with high frequency resonating charnbers for attenuating high frequency sound waves and a resonator or resonating chamber of the so-called dead type for attenuating low 4frequency sound waves principally by sound absorption. The low frequency resonator or chamber, in effect, provides a sound trap in which low frequency sound Waves are substantially dissipated by absorption.' In muffler constructions embodying a dead low frequency sound attenuating chamber, the exhaust gases do not circulate through this chamber even though it is disposed with respect to the gas stream so that low frequency waves enter and are dissipated or attenuated therein.

While sound attenuating constructions of this character have been used, they have several dis-advantages. The length of the mufller is relied upon to attenuate a substantial proportion of sound waves in an exhaust gas stream, and the employment of one or more low frequency chambers disposed so that the exhaust gases do not flow through the chamber or chambers limits or decreases the effective length of the sound attenuating systern thereby limiting the range of sound wave attenuation. Exhaust gases of internal combustion engines are usually very hot, with temperatures upwards of 12010" F. or more and the gas passage tubes and walls of the mutller construction in direct contact with the gases become highly heated while the dead, resonator chamber is at much lower temperatures because of lack of circulation or movement o-f exhaust gases therethrough. Thus, within a muler of this character, extreme temperature differentials exist and, upon cooling vof the mufller, condensation of moisture takes place particular-ly in the dead cham ber and the formation of rust and deterioration are augmented, and the useful life of such a muffler shortened where the components of the muler construction are fabricated of ferrous metals.

The present invention embraces the provision of a muler construction or sound attenuating means usable with a moving gas stream wherein the gases of the stream are circulated throughout all of the interior regions of the muffler construction, the muffler embodying low frequency sound attenuating chambers arranged whereby circulation of gases ltakes place in the low frequency sound attenuating chambers.

The invention has for an object the provision of a sound attenuating apparatus or muffler wherein the sound attenuating system includes gas passage means in conjunction With low frequency resonators or sound wave attenuating chambers disposed in adjacent relation with a connecting medium between the resonators proportioned or tuned to provide for the attenuation of sound waves of a desired ran-ge of frequencies.

increased range of frequencies may be attenuated ythe resonators are formed by a common wall or baffle and are connected by a tuning coupling which may be proportioned or adjusted to vary the frequency range of attenuation of 4the resonators in conjunction with gas passage. mea-ns in the mufller arranged whereby gases moving through the muffler are circulated through the resonators to establish substantially uniform temperature .throughout the various regions of the muiiler construction to minimize the condensation of moisture.

Another. object of the invention resides in the provision o-f a muler embodying gas passage means and sound attenuation means of substantial length including'dual low frequency resonator chambers arranged whereby an Without enlarging the muler construction.

Still another object of the invention is the provision of a multi-pass muffler embodying dual low frequency -sound attenuating chambers, high frequency attenuating means and gas passage means incombination With partitions arranged ywhereby all of the interior regions of the mufller construction are directly subjected to heat from the exhaust gas stream and the circulating exhaust gases preventing or minimizing the formation of moisture condensation within the mufller and reducing temperature differentials within the mufer.

Further objects and advantages are within the scope of this invention such as rela-te -to the arrangement, operation and function of the related elements of the structure,4to various details of construction and to combinations of parts, elements per se, and to economies of manufacture and numerous other'features as will be apparent from a consideration of the specification and drawing of a form of the invention, which may be preferred, in which:

FIGURE 1 is a longitudinal sectional view of a mufiler Iconstruction of the invention, the view being 4taken substantially on the'line 1 1 of FIGURE 2;

FIGURE 2 yfis an enlarged transverse sectional view taken substantially on the line Z-Z of FIGURE 1;

FIGURE 3 isha fragmentary detail sectional view illustrating a modilication of a portion of the construction shown in FIGURE 2;

FIGURE `4 is a schematic longitudinal sectional view illustrating another Iform of the muffler construction of oval cross section of the invention;

FIGURE 5 is a schematic longitudinal sectional view illustrating another form of mufller construction of oval crosssection of the invention;

FIGURE 6 is a schematic longitudinal lsectional view `illustrating another form of muiller construction of oval lcross section of the invention; and

FIGURE 7 is a schematic longitudinal sectional view illustrating a further form of muffler construction of oval cross section of the invention.

While the preferred arrangements or constructions of the invention illustrated in the drawings are of the type or character particularly adapted for attenuating and absorbing sound waves entrained in exhaust gais streams from internal combustion engines, it is to be understood that the principles of the invention may be utilized in other forms of sound attenuator or silencer.

Referring to the drawings in detail and initially to the v construction shown in FIGURES 1 and 2, the muler is inclusive of an elongated housing, casing or shell 10 preferably of the double wall type comprising an inner layer of sheet metal 12 and an outerV layer 14` of sheet metal. The inner landouter layens 12 and 14 are preferably of independentsheets of metalV but it is to be understood that the shell construction of the muffler may be a single wall or a double wall wherein a single sheet .of metal is rolled upon itself with indentatiocns or ridges f 3 spacing the overlapping regions of the multiple Wall construction. v

As particularlyrshown in FIGURE 2, the outer layer 14 is formed with inwardly extending iiutes or recesses 16 arranged longitudinally of the shell or housing and spaced circumferentially to provide inwardly extending ridges which engage the inner layer 12 to space the inner and outer layers or sheets as shown in FIGURE 2.

fIhe meeting edge regions of the inner and outer layers are foldedvor bent upon themselves to form an interlock or longitudinally extending bead as at 18, the folded or bent portions of the sheets being crimped to form a fluid- `tight seam or juncture extending lengthwiser of the muffler construction.

it is found-that aldouble walled arrangement for the muier shell or housing reduces to a large extent so-called shell noise. As particularly shown in FIGURE 2, the

' cross-.sectional configuration or shape of the muffler construction or shell is generally oval or ellipsoidal, but it is to be understood that the shell or casing cross-sectional configuration may be circular or other shape if desired.

The shell or casing construction is provided with end walls, heads or closures `20` and 22 of sheet metal, each of the heads or closures being formed with a peripheral flange configuration 24 of generally U-shaped cross-section providing a peripheral recess or groove which receives they mating or engaging end regions of the shell walls or layers |12 and 14 in the manner shown in FIGURE 1. It should be noted that the end regions of the layers 12 and 1'4 are brought into contiguous engagement and are embraced in the respective recesses provided by the liange constructions 24.

i ings to accommodate an inlet gas passage means or tube yIn assembly, the outermost ange portion is crimped Thev longitudinally extending chambers 26 are isolated 'from the interiorV region defined by the inner shell wall 12 of the mufer construction, the confined zones or elongated chambers 26 forming individual air cushions Which assist in reducing shell noise or vibration. The end closure or head 20 at'the inlet end of the muflier is formed with a circular flange 28 defining an opening adapted to accommodate a coupling sleeve or tubular fitting 30 extendingtherethrough as shown in FIGURE 1";

The portion of the iitting 30 exteriorly of the end head 20 is formed `with a slot 32, and is adapted to be telescoped with an exhaust pipe from an engine, and a clamping means (not shown) applied to this region of the tting to draw the iitting into snug engagement with the exhaust pipe. The end head 22 is formed with an opening def fined by a circular flange 36, the opening adapted to accommodate a coupling sleeve or tubular fitting 38 of the same `type as the coupling 30.

The coupling 38 at its end region is formed o` r prov vided with a slot 40 and is adapted to be telescoped with a tail pipe for conveying gases away from the muliier,

a clamp (not shown) being adapted to surround the end region of the coupling 38 to clamp the same to the exhaust discharge pipe.

In the arrangement illustrated in FIGURE 11, the tittings or couplings 30 and 38 function as portions of inlet gas passage means and outlet gaspassage means for conveying exhaust gases into and out of the interior of the muiiler.y y a f p u Disposed within the interior of the muflier are longi-v tudinally'spaced transversely extending partitions, walls or headers 42, `44 and 46. In the embodiment illustrated `the headers 42, 44 and I46 are provided with aligned open- 48, the inlet end being telescoped into the coupling 30'. The tube 48 is formed of a -sheet of metal with the edge regions interlocked as shown at `49 in FIGURE 2. The wall or partition 46 is spaced from the end closure or head `2.2 providing a chamber 50 accommodating transverse flow of exhaust gases and providing a rlow frequency resonator or chamber for attenuating or absorbing low frequency sound waves. The inlet gas passage means 48 extends into the chamber 50.

The partitions or headers 42, 44 and 46 are provided with aligned openings to accommodate a second gas passage means or tube 5'4. The end closure A20 and the partition 42 deiine a low frequency resonator or chamber 56, the partitionsl-Z and 44 delining a second low frequency resonator 58 which is adjacent the resonator 56. The partitions 44 and 46 define a chamber 60. One end of the second gas passage means or tube 54 opens into the transverse gas passage chamber 50, the other end opening into and extending about midwayin the low frequency resonator 56.

'Ilhe transversely extending partitions `44 and 46 are formed with openingsV to accommodate -a gas passage means or tube 62 one end of which extends a substantial distante into the resonator or chamber 58, the 'other end being telescoped into the coupling 38 providing a `gas discharge lmeans from the muler. The header or partition 42 defining |a wall of e'afch of the low rfrequency resonators 56 `and 58 is provided with an opening accommodating a frequency `attenuating rangey modifying medium or .tuning tube 64, portions of which extend substantial distances into the resonators 56 and 58 las .shown in FIG- URE l. Each of Ithe tubes 54 land 62 istfalshioned of a sheet-of metal with the edges overlapping as sho'wn at 63 in FIGURE 2 and secured together as by welding.

'I`he length and diameter of the tuning .tube 'controls the (frequency range of attenuation of the resonators 56 and 58 to modify within limits the resonant frequencies of these chambers. lMeans is ldisposed between the parti-V tions 44 and 46 and cooperating 'with the gas passage means extending through the region between these partitions providing thigh frequency sound Iattenuating chambers. VExtending lengthwise of the muffler between op posi-ngwalll portions ot the inner layer 12 and adjacent y the tube or gas passage means 54 is a Ibailie or partition 66 provided with liange portions 63 Welded to the inner layer 12 Ias shown in FIGURE 2 yand 'having its ends joined with the partitions 44 yand 46. n

Through the use of the lengthwisey partition 66, the region of the gas passage tube 54 between the headers 44 and 46 is isolated from adjacent overlapping @regions of the tubes 48 Kand. 62. The Walls of the gas passage tubes between the headers 44 and 46 are provided 'with ecmparatively -llarge numbers of small openings 70, 72 and 74 which torni acoustic couplings |with the regions sur-` rounding and yadj-acent the respective tubes. Thus the partition 66 forms with ya portion of the inner shell 12 a thigh frequency sound lattenuating chamber 76 for attenuating high frequency sound waves.

A partition 78 similar to partition 66 extends lengthwise of the muffler between 'opposed 'wall portions oi the inner layer 12 asr shown in FIGURE 2 Iand is provided with flanges 80 lwelded to the inner layer and having its ends joined with the partitions 44 and 46. 'Ilhe partition 78, with the adjacent wali portions of the inner shell or layer 12 provide a high frequency sound lattenuating dhamber S2 `adjacent the perforated region oi the gas. passage means 62 as shown in FIGURE 2.

'Ilhe region between `the partitions 66 yand 7S forms a high frequency sound lattenuating chamber 84 'which is isolated from the -hi-gh frequency lattenuating chambers 76 and 82. It should be noted that fthe small openings'v :for the circulation of exhaust gases through the respective high frequency sound attenuating chambers.

`In this manner the exhaust gases flow `into the respective high frequency sound attenuating chambers and into the gas passage means passing tln'ough the chambers so that f the exhaust gases are not trapped or held within the frequency attenua-ting chambers. Through this arrangement the yexhaust gases circulate through the high frequency sound attenuating chambers with little variation .in the temperatures of the metal walls defining the chambers.

An important feature of the present invention is the provision of the dual low tfrequency resonators 56 and 58 arranged in ladjacent relation and connected hy la tuning tube 64. The provision of the tuning tube `64 facilitates the modification of the frequency attenuating range of the low [frequency resonators to secure most effective sound attenuation of low :frequency sound waves in a particular exhaust gas stream.

The length and the diameter of the tuning tube 64 modifies the :frequency range of attenuation of the resonators 56 and 58. By shortening ythe tuning tube 64, the resonators 56 and 58 attenuate or absorb higher frequenoy sound Waves and lengthening the tube lowers the range of 'frequencies attenuated or absorbed in these chambers. By using a smaller diameter tuning tube 64, the resonators attenuate sounds of lower frequencies and, conversely, a tuning tube of larger diameter, higher sound rirequencies are attenuated, absorbed or damped hy the resonators 56 and 58. The tuning tube 64 however should be of suflioient diameter to avoid increasing back pressure in the enlraust gas stream moving through the muffler.

In the operation of the muffler shownin FIGURES 1 and 2, the exhaust gases or the gases of a stream oW into the muiler through the ygas passage means 48 into the transverse gas passage or chamber 50, thence in a reverse vdirection through the gas passage tube 54 into the resonator 56, through the tuning tube V64, resonator 58 and the outlet tube or Igas passage means 62 whereby the gases 'are 'conveyed away from the muffler. lIt should be noted that the Wall region of the tube 48 extending through the resonator chambers 56 and 58 is unperiorated and the region of the intermediate gas passage means or tube 54 adjacent the resonator chamber 58 is unperlforated.

I-n this manner the exhaust gases are caused to flow through all interior regions of the muflier dened'by the inner layer or shell 12 and the end heads 20 and 22 so that there is a substantially uniform Vternp'eratureof all components of the muier under the iniluen'ce of .the heat (from the exhaust gases.

Through this arrangement there are no pockets or dead chambers, that is, chambers in Iwhich exhaust gases do not circulate, so that there are no regions of extreme 4temperature differentials within the muffler. 4

rEhe use of the tuning tube 64 facilitates the adjustment of effective attenuation of desired ranges of low frequency sound waves in they low rfrequency resonators "56 and 58. perature differentials throughout various regions of the muler construction, the tendency for the formation of condensation the muler is ygreatly reduced, minimiz- `ing the liability of corrosion vand oxidation and hence providing lfor an increased life of the muffler construction.

FIGURE 3 is -a fragmentary sectional view illustrating a modified form of means surrounding a glas passage tube or gas passage means providing a [frequency sound wave attenuating chamber. In this form of construction, ithe gas passage tube 62 is surrounded by 1a cylindrical shell or intermediate tube 88, in'lieu of the partition 78 Ashown in FIGURES 1 `and 2, which nts the curvature of the inner shell at the longer dimension of the ellipsoidal configuration. The .tube 88 is 'formed oi -a sheet of metal with the edges overlapping as indicated at 89` and secured .togetheras hy welding. The housing `construction is of By reducing the likelihood or severe tem-.

the same character as illustrated in FIGURE l, the inner shell 12 being contiguous with the intermediate shell throughout approximately one half of the peripheral span of the intermediate tube. The partition or intermediate shell or tube 88 is welded or otherwise secured to the transverse headers so as to maintain the intermediate tube 88 in proper position in the muler. It is to be understood that a tube of the character shown at l88 may be employed with the tube 54 shown in the construction of FIGURE 2, providing a high frequency sound wave `attenuatingidhamber.

FIGURE 4 illustrates a modified form of the invention. This form of muller construction comprises a dual wall shell, casing or housing provided with end heads or closures 102 land 104 which are joined to the housing in the manner shown and described in connection with the form of the invention illustrated in FIGURES 1 and 2. The end head 102 is provided with 1an oicenter opening accommodating an inlet 'gas passage means or tube 106. The end head 10'4 is provided with a central opening accommodating a Agas passage means or outlet tube 108.

lDisposed within the housing 100 are transversely extending walls or partitions 110, 111 and 112 'which are longitudinally spaced as illustrated. The ygas passage inlet means or .tube 106 extends through openings in all three of the partitions and opens into a lgas transfer chamber 114 formed by the partition 1121and the end head 104. rIhe region between the end head 102` yand the partition provides a low frequency sound `attenuating resonator or chamber 116, vand the partitions 110 and 111 dene la second `low frequency sound attenuating resonator or chamber 118, the low frequency resonators ybeing 'arranged in adjacent relation.

A third gas passage means or tube extends through openings in the three partitions 110, 111, 112, one end of the rgas passage means 120 `opening into the gas transfer passage orchamber 114, the other end opening into the low yfrequency resonator 116.

It should be noted that the gas outlet passage means 108 extends a substantial distance into the low frequency resv onator 118. 'Ihe partition 110 disposed between the low frequency resonators is provided with an opening to receive a -gas passage tube 122, the latter extending sub stantilall distances into the resonators 116 and 118.

The extremity of the tube 122 in the resonator 118 is spaced -a `substantial distance rfrom the inner end oi the gas passage outlet tube 108. The tube 122 provides a tuning means between the low frequency resonators 116 and 118, the length and size otf which modies the range of low frequency sound waves attenuated in the low frequency resonators. The wall portions .of the gas passage tubes 106, 108 and 120` in overlapping relation between the partitions or 'transversely extending walls 111 and 112 are provided with a comparatively large number of small openings 123.

The perforated region of the tube 108 is isolated from the perforated regions of the gas passage tubes 106 and 120 by lengthwise extending partitions or separators 1214 land 126 which may be of the character of the lengthwise partitions 66 and 78 in the tform of the invention of FIG- URES l and 2. lIt is to be understood that the isolation of the perforated region of the tube 108 may be attained vthrough the use of intermediate cylindrical shells or tubes surrounding the perforated portions of tubes 106 and 120 in the manner illustrated in FIGURE 3.

Through the isolation of the perforated regions of each of the three tubes disposed between the partitions 111 kand 112, high frequency sound attenuating chambers 127, 128 Iand .150 Iareprovided at the perforated regions of the tubes. The openings in the tube wall-s provide acoustic couplings with the high frequency sou-nd attenuating chambers surrounding the perforated portions of the tubes and means to facilitate the circulation of lgases through the chambers 127, 128 and 130.

The portion ofthe gas passage tube 110 between the i' shown in FIGURE 4, the gas stream, such as an exhaust gas stream from an internal combustion engine, enters the inlet v'gas passage tube 106, the gases flowing into the transverse gas passage or 'chamber 114, some of the gases of the stream flowing through the perforations in the tube 106 and circulating through the high frequency attenuating chamber 128.

i "Ihe gases flow transversely through the gas .transfer passage 114, thence ina reverse direction through the gas passage means or tube 120 into the low frequency resonators 116, some of the gases entering the perforations or openings in Ithe tube 120 and circulating through the high frequency sound lattenuating chamber 130. The gases in the low -frequency resonator 116 flow in ia .righthand direction through the tuning tube 122, circulating through the low frequency resonator 118 and are discharged from thefmufller through the outletv gas .passage tube 108.

` Some of the gases circulate through the high frequency chamber 127 surrounding a portion of the outlet tube 108. Thus it will be seen that gases moving thro-ugh the muffler flow into and circulate through yal1 of the chambers and passages so that `a substantially uniform temperature obtains throughout all the interior regions of the muliler construction. The tuning tube 122 may be modified in size and length to inuence the range of :low frequency sound waves attenuated in the low frequency resonators 116 and 118.

FIGURE 5 illustrates another form of muffler construction of the invention. In this form the muflier preferably includes a double wall shell or casing 140 provided with end heads 142 and 143. The construction includes a gas passage means l144 extending through the end head 142 forming the gas inlet, a second ygas passage means 146 extending through an `opening in the end head 143 providing a gas ,discharge means for the muffler. In this form of construction, the inlet tube is offset from the central axis of the muffler and the outlet tube 146 is substantially on the central axis of the muflier.

Disposed within the shell 140 are transversely extending partitions or Walls 145, 147 and 148 spaced longitudinally as illustrated.' The inlet tube 144 extends through aligned openings in the three partitions and the outlet tube 146 extends parallel with the tube 144 through aligned openings in the several partitions. A third lgas passage tube 150 extends through openings provided in the partitions 145 and 147. rIhe partition 145 with the end head 142 delines a transverse gas transfer passage 152.

'Ihe partition 148 with the end head 143 defines a low v frequency resonator or chamber 154 and the partitions 147 and 148 define a second low frequency resonator 156, the low -frequency resonators being arranged in adjacent relation. The gas passage means or tubes 144, 146 and 150 are inoverlapping relation and the Walls of they overlapping portions of these Itubes disposed between the partitions 145 and 147 are provided with a comparatively large number of small openings 149 forming acoustic couplings with the adjacent regions.

Disposed between the overlapping portions of the tubes and extending lengthwise between the transverse partitions 145 and 147 are lengthwise disposed partitions, separators or batiies 158 and 160 which may be of the character of the separators or baffles 66 and 78 in the construction illustrated in `FIGURES 1 `and 2. These lengthwise partitions isolate the overlapping perforated portions of each lof the tubes 144, 146 and 150 between the partitions 145 and 147 and provide high frequency sound attenuating chambers, one chamber being adjacent to each of the perforated overlapping regions of the tubes.

The IWall portion of the outlet tube 146 disposed between the partitions 147 and 148 is provided with a large `number of small openings 157 and this por-tion of the tube is surrounded by an intermediate cylindrical shell or tubular member 164. The annular space between the adjacent portion of the tube 146 and the intermediate shell 164 provides `an additional high `frequency sound attenuating chamber 165.

Extending through an opening in the partition 148 isY vides a means for modifying the range of low frequency i sound waves attenuated in the lresonators 154 and 15.6.

In the operation of this form of construction the gases enter the inlet ygas passage means 144 and ilow into the low frequency resonator 154, some of the gases circulating through the high frequency sound attenuating chamber surrounding the perforated portion vof the tube 144. The -gases flow from the resonator 154 through the tuning tube 166 into and circulate in the second low frequency res- -onator 156 thence through the .gas passage tube 150 into the gas transfer passage 152 and into the outlet tube 146 which conveys the exhaust gas out of the muffler.

The gases circulate through 4the high Ifrequency sound attentuating chambers surrounding the perforated regions of the tubes 144, 146 and 156 so that the exhaust gases circulate throughout the entire interior regions of the muffler `and thereby establish substantially uniform temperature throughout the muffler. Through the establishment of a more uniform temperature, the 4liability of cold regions existing in the muffler, which foster the formation of condensation, are avoided thus prolonging the 'life ol the muffler construction.

=It should be noted in this form that the first low frequency' resonator 154 is adjacent the end head 143 at the outlet region of the muffler and the second low frequency resonator 156 is adjacent the rst low =frequency resonator.

In the arrangement shown in FIGURE 5, `an increased Zone of high frequency sound attenuation is provided through the `added chamber defined by the intermediate `tube or shell 164 surrounding an additional perforated portion of the tube i146 between the partitions 147 and 148.

FIGURE 6 is illustrative of `another form of muffler construction of the invention. The muffler construction of FIGURE 6 preferably includes la l uble wall shell or casing provided with .end heads 172 and 174. The construction includes transversely extending longitudinally spaced walls, partitions or headers 176, 177 and 178. An inlet gas passage means or tube extends ythrough opening-s in the partitions and open-s into la low frequency resonator chamber 182 ldefined by the end head 174 and partition 178. g

A gas passage means 184 forming 4an outlet for the gases extends through the end head 174 :and through aligned openings in the partitions. The end of tube 184 opens into a gas transfer passage 186 defined by the end heard 172 and the partition 176. A second low frequency resonator 188 is defined by the partitions 177 and 178. A

third gas passage mea-ns or tube 190 extends through openings in the partitions 176 and 177, one end of tube 190 opening into Ithe gas transfer passage 186, the other end thereof opening into Aand yextending `a substantial distance in the low frequency resonator 188.

A tuning tube 192 extends through an opening in the partition 178, the tube extending substantially into both resonators 182 and 1'88. 'Ihe length of the tube 192 or its `size or both may be varied to modify the range of low frequency sound Waves attenuated or absorbed in the v shown in FIGURE 2. 'The partitions 196 and 198 isolate each of the overlapping portions of the tubes between the 'partitions '176 and 177 forming three high frequency sound :attenuating chambers 199, 200 @and 201. Theregions of the tubes 180 land 184 between the partitions 177 and .178 are perforated with a large number of small openings 202 forming acoustic couplings with the adjacent regions.

These perforated portions of thetubes -1180 Iand 184 are each surrounded by an intermediate circular shell 204 which extends between the partitions y177 and -178 and form highr frequencysound attenuating chambers 206 `an-d 208. The intermediate shells 204 form side Walls of the low frequency resonator i188; iIt Vshould be noted Y that in this form of the invention there are live high frequency'sound wave attenu-ating chambers and two low frequency resonators -182 and i188, the latter being in adjacent relation.

In the operation of this form of construction, the exhaust .gases enter the inlet tube 180, the gases flowing into the low frequency resonator 182, Isome of the gases flowing through the openings or perforations y194 and 202, circulating through the adjacent high :frequency attenuating cham-bers, such circulating gases re-entering the tube 180 and flowing into the resonator 182. The gases in the low frequency resonator 18.2 fiow in a reverse direction through the tuningtube 192, circulating through the second low frequency resonator 188 thence through the gas passage tube 190 into the gas transfer passage 186.

The gases in `the transfer passage 186 lio-w into the outlet tube :184 and away from the muflier. The gases moving through 4the perforated lregions of the several tubes or gas passage means circulate through the high frequency attenuating chambers adjacent the perforated kregions so that the gasesrnoving through the muffler circulate throughout the entire regions interiorly of the muler thus establishing a substantially uniform temperature throughout the interior of the muler.

It should be noted that :all of the gases must flow through the tube 180 into the resonator 182 thence into the gas transfer passage 1186 and through the full length of the outlet tube 1184. In this manner all of the gases traverse substantially full length of the muffler, moving in a substantially S-s-haped path. It should be noted that in this form of construction live high frequency sound attenuating chambers Iare provided for attenuating high frequency sound waves.

FIGURE 7 illustrates still another form of the muffler construction of the invention. IIn this form the muffler preferably includes a double wall shell 220 provided with end heads 222 and 224. Disposed interiorly of the shell 220 |are four transversely extending 'walls or partitions 226, 227, 228 and 229, which Iare spaced lengthwise of the shell or housing. An inlet gas passage means or tube 230 extends through an opening in the end head 222 and through kan opening in the partition 226 and opens into a low frequency resonator 232.

-A second gas passage tube or outlet tube 234 extends through an opening in the end head 2,24 and through j openings in the partitions or 'walls 228 and 229, one end of the tube opening into a transverse gas passage or chamber 236. A third gas passage means or tube 238 extends through openings in partitions 226, 227, 228 and 229, one end of the tube opening into la second gas trasfer passage 240 defined by the end head 224 and the partition 229, the other end of the tube 238 opening into a second 'low frequency resonator or chamber 242.

Another gas passage means or tube 244 extends through openings in the partitions 228 and 229, the respective ends of tube 244 opening into the gas transfer passages 236 yand 240. A tuning tube 246 extends through an opening in the partition 226 and establishes communication between lthe two low frequency resonators 232 4and 242, the tube 246 extending `a substantial distance into each of the resonators. The length or size of the tuning 10 tube 246 may be changed in onder to vary the range of frequency of sound waves absorbed in the low frequency resonators 232 and 242.

The portion of the tube 238 within the low frequency resonator 232 is provided with a comparatively large number of small openings v248. Extending lengthwise `between the partitions 226 and 227 `is La longitudinal partition or separator 250 which forms a Wall of the low frequency resonator 232 and isolates the perforated region of tube 238 between partitions 226 and 227, Iform- :frequency sound Wave attenuators 262, 264 and 266.

Thus in this form of construction there lare four high frequency sound Wave lattenuating chambers.

The operation of -this form o-f construction is as follows: The exhaust :gases 'enter -the inlet tube or gas passage means 230 and flow into the resonator chamber 232. The gases in the resonator chamber 232 flow in a reverse direction through the tuning tube 246 into the second resonator chamber 242.y The gases in the resonator 242. flow through the gas passage tube 238 into the gas transfer chamber 240, thence in a reverse direction through the tube '244 into the second gas `transfer passage 236. The gases in the transfer passage 236 ilo'w through the exhaust outlet tube 234 and away from the muffler.

Some of the gases flowing through the perforated regions of the gas passage tubes enter the high frequency sound attenuator chambers adjacent the tubes so that *there is a circulation of :gases throughout the entire interior regions of the muffler establishing a substantially uniform temperature throughout the entire interior regions .of the muffler.

By shortening the tuning tube in the forms of the invention the range of frequencies attenuated is increased. By making the diameter of the tuning tube smaller or lengthening the tube the range of frequencies yof sound waves attenuated is lowered.

It is apparent that, within the scope of the invention, modications and different arrangementsl may be made other than as herein disclosed, and the present disclosure is illustrative merely, the invention comprehending all variations thereof.

I cla-im:

l. A muler for use with a moving gas stream including, in combination, an elongated tubular shell provided with end walls, a plurality of longitudinally spaced transverse walls intermediate the end walls in said shell and extending completely across the inside of the shell, certain of sai-d Walls defining dual low frequency resonators and transverse gas transfer means, said dual resonators being arranged in adjacent relation, said Igas transfer means being spaced from the low frequency resonators, a plurality of gas passage means extending lengthwise in said shell, one of said gas passage means providing Ia gas inlet and another of said gas passage means providing a .gas out-let for the shell, a third gas passage means connecting said gas transfer means 'with one of the low frequency resonators, and a tuning tube disposed in an opening in the wall intermediate the dual low .frequency resonators and extending a substantial distance into each of the resonators, said gas transfer means and said low Ifrequency resonators and third gas passage means being arranged whereby gases moving through the muler 4iofw through both low :frequency resonators in sequence.

2. A sound yattenuatin-g means Ifoi use with a gas stream, in combination, an elongated tubular housing, end walls secured to the housing, said end walls being provided with gas inlet and outlet openings, a gas passage tube in said Yhousing' inregistration with the inlet opening, a second gas passage tube in said housin-g in registration with the outlet opening, a plurality of transversely extending,

Alongitudinally spaced intermediate walls in said housing,

one of said Walls being disposed between another of said walls yand-an end wall Iand defining two adjacent low -ire- Aqu-ency resonators, the opposite end wall Iand the `adjacent intermediate wall forminga transverse lgas passage means,

4an open ended pipe extending through the wall between the resonators and projecting a substantial distance into Veach resonator, and a third gas passage tube in said housstream, 4in combination, an'elongated tubular shell, end

heads secured to the shell, an inlet gas passage tube extending through one of said heads into the shell, an outlet gas passage tube in said shell extending through the other `end head, at least two transversely -disposed longitudinally spaced partitions in said shell ideining with one of said end heads a pair of low frequency resonator chambers, a ytuning tube extending through the partition between the chambers and projecting a substantial distance into each chamber, transverse gas passage means in said shell formed by the other end head and an adjacent partition, and a third gas passage tube in communication with the transverse gas passage means and one of the low yfrequency resonators arranged to direct all of the gases from the inlet gas passage means into the resonator chambers for disch-ange throughthe outlet gas passage mean-s.

4. A sound attenuating means for use with a gas stream, in combination, a tubular shell, end heads secured to the shell, a gas inlet tube in said shell extending `through -an opening in one of said heads, a gas outlet tube in said shell extending through an opening in the other of the heads, a third tube in said shell arranged in .transverse overlapping relation with said inlet and outlet tubes, a plurality of transversely disposed partitions in said shells extending completely Iacross the inside of the shell, two ot said partitions and lan end head defining two low -freqnency resonatorcharnbers in adjacent relation, a tuning tube disposed in an openingin the parti tion intermediate the low4 frequency resonator chambers,

the Walls of the overlapping regions of said tubes between two yof said partitions being provided with fa comparatively large number of perforations, lengthwise extending bale means separating the perforated overlapping regions of the tubes one from another forming high frequency sound attenuating chambers, a transverse gas transfer passage yformed by the opposite end head and `an adjacent partition establishing communication 'with two of said tubes providing for ow of ygases through said two tubes in opposite directions `and through the low frequency resonator chambers in sequence, said perforations in the `overlapping portions olf said tubes forming acoustic couplings with the high frequency sound attenuating chambers.

References Citedin the le of this patent UNITED STATES PATENTS 2,070,543 Cary et al. Feb. 9, 1937 2,111,537y Noblitt et al Mar. l5, 1938 2,116,751 Deremer May 10, 1938 2,182,405 Noblitt et al Dec. 5, y1939 2,193,791 Hollerith etal Mar. :19, .1940 2,357,791 Powers Sept. 5, 1944 2,618,354 Hedrick Nov. l118, 1952 2,652,128 Cary Sept. `15, 1953 2,661,073 Deremer Dec. 1, 1953 2,950,777 Deremer Aug; 30, 1960 2,958,389" Deremer Nov` 1,1960 

1. A MUFFLER FOR USE WITH A MOVING GAS STREAM INCLUDING, IN COMBINATION, AN ELONGATED TUBULAR SHELL PROVIDED WITH END WALLS, A PLURALITY OF LONGITUDINALLY SPACED TRANSVERSE WALLS INTERMEDIATE THE END WALLS IN SAID SHELL AND EXTENDING COMPLETELY ACROSS THE INSIDE OF THE SHELL, CERTAIN OF SAID WALLS DEFINING DUAL LOW FREQUENCY RESONATORS AND TRANSVERSE GAS TRANSFER MEANS, SAID DUAL RESONATORS BEING ARRANGED IN ADJACENT RELATION, SAID GAS TRANSFER MEANS BEING SPACED FROM THE LOW FREQUENCY RESONATORS, A PLURALITY OF GAS PASSAGE MEANS EXTENDING LENGTHWISE IN SAID SHELL, ONE OF SAID GAS PASSAGE MEANS PROVIDING A GAS INLET AND ANOTHER OF SAID GAS PASSAGE MEANS PROVIDING A GAS OUTLET FOR THE SHELL, A THIRD GAS PASSAGE MEANS CONNECTING SAID GAS TRANSFER MEANS WITH ONE OF THE LOW FREQUENCY RESONATORS, AND A TUNING TUBE DISPOSED IN AN OPENING IN THE WALL INTERMEDIATE THE DUAL LOW FREQUENCY RESONATORS AND EXTENDING A SUBSTANTIAL DISTANCE INTO EACH OF THE RESONATORS, SAID GAS TRANSFER MEANS AND SAID LOW FREQUENCY RESONATORS AND THIRD GAS PASSAGE MEANS BEING ARRANGED WHEREBY GASES MOVING THROUGH THE MUFFLER FLOW THROUGH BOTH LOW FREQUENCY RESONATORS IN SEQUENCE. 